The THUMS TM Human Models - Overview - Dirk Fressmann DYNAmore GmbH - - PowerPoint PPT Presentation

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The THUMS TM Human Models - Overview - Dirk Fressmann DYNAmore GmbH - - PowerPoint PPT Presentation

Jan 16, 2023 211 likes •589 views

The THUMS TM Human Models - Overview - Dirk Fressmann DYNAmore GmbH Infotag Human Modeling Stuttgart, Juni 2016 Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH 1 Human Models developed as direct model of the

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

The THUMSTM Human Models

  • Overview -

Dirk Fressmann

DYNAmore GmbH Infotag Human Modeling Stuttgart, Juni 2016

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

  • developed as direct model of the human body
  • represent additional tools to evaluate injury risks and

develop/improve passive and active safety systems

  • „vehicle optimisation w.r.t. to humans, rather than dummies“
  • reproduce anatomical geometry and biomechanical properties
  • f the human body
  • e.g. geometry, skeletal structure, joints, stiffness- and mass distribution, etc.
  • AM50, AM95, AF05, 6YO, (individual)
  • are used in crash, ergonomics, seating

comfort, sport sciences, etc.

  • simulation of the kinematics
  • f the human body
  • stress- and strain evaluations

in bones and joints

  • recent, more detailed models

may also allow deeper analysis

  • f organ injuries or more general

injury mechanisms

Human Models …

Comparison WorldSID, Hybrid III, THUMS V3, THUMS V4

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Experiment Numerical Simulation Crash Test Dummy human numerical human model numerical dummy- model

Model Model

Model

  • From human to dummy and to virtual dummy model
  • From human to virtual (numerical) human model

From Dummy to Human Model permanent development

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Available Human Models

  • THUMSTM – Total HUman Model for Safety
  • developed by Toyota Motor Corporation and Toyota Central R&D Labs. Inc. since 2000
  • additional research institutes involved (e.g. WSU, Detroit/Michigan)
  • 2 versions with 2 levels of detailing

simplified and detailed GHBMC occupant models [Courtesy by www.ghbmc.com] THUMS V4 pedestrian and occupant models

  • GHBMC-Models – Global Human Body Model Consortium
  • Members: Chrysler, GM, Honda, Hyundai, Nissan, Peugeot, Renault, Takata
  • development at various US universities (Wake Forest, Uni of Virginia, Uni Waterloo,

IFSTTAR)

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

  • Versions
  • 1.0

– first version (since ~2000)

  • 1.4/1.6

– first usable generation (since 2004)

  • 3.0

– third generation (beginning of 2008)

  • 4.0x

– fourth (current) generation (end 2010) current version: Version 4.02

  • Version 5.0

– based on Version 3, including muscle modeling

  • academic and commercial versions available
  • only civil usage permitted

THUMS V1.x THUMS V3 THUMS V4.02 THUMS V4

Model Variants and Versions

THUMS V5, relaxed and braced state

not available anymore

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

THUMS Occupant Model

  • occupant simulations, belt

development, airbags, etc.

  • higher biofidelity

→ front/side/rear crash situations

  • driver & co-driver postures
  • interest in “THUMS Family”

AM95, AM50, AF05, etc. THUMS Pedestrian Model

  • pedestrian safety simulations (head impact time

and location, qualitative injury evaluation)

  • variation of posture, stance or model size
  • additional interest in „THUMS Family“

(different model sizes – AM95, AM50, AF05, 6YO, ...)

  • basically same modelling techniques for occupant and

pedestrian with slight modifications (V3: internal organs, shoulder, material properties + failure behaviour)

Model Variants and Versions

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

THUMS Model Versions 1.x and 3.0

Model Variants and Versions

enhanced head model THUMS V3 simple head model THUMS V1.x

Versions 1.4/1.6 (ca. 2004-06)

  • kinematical model (skeletal structure, joints,

flesh, simplified organs, simple head model)

Version 3.0 (beginning of 2008)

  • refined head model (based on CT-scans)
  • also: material adaptations, slight

geometrical changes

  • theoretically head injury simulations

possible

  • mostly based on literature data (geometry and material properties)
  • simple materials (mostly elastic, elastic-plastic, viscoelastic)
  • AM50 model size, comparable to size of corresponding dummy models
  • exclusively used for kinematical evaluations

THUMS 1st Generation Version 1.x THUMS 2nd Generation Version 3.0

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

  • no model update → new model rebuilt from scratch
  • geometry obtained from medical CT scans
  • basis: 39 year-old male (173cm, 77.3kg, BMI 25.8)
  • scaled to AM50 model (178.6cm, 74.3kg) → realistic geometry
  • very high detailing of joints, internal organs, head, …
  • model parameters
  • element size 3-5mm, 1.8Mio elements, 630,000 nodes
  • mainly solid elements (hexa/tetra mesh) and some shell meshing

Current Version: THUMS Model Version 4.x

Model Variants and Versions

  • ccupant upper body

pedestrian thorax THUMS 4 occupant and pedestrian models

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

THUMS

  • ccupant

models THUMS V1.61

(not available)

THUMS V3.0

(not available)

THUMS V4.0 THUMS V4.02

(current)

parts 1,350 1,576 1,273 1,293 nodes 66,729 104,489 628,358 762,997 elements

  • deformable
  • rigid

91,204 70,019 21,185 143,044 118,484 24,560 1,755,284 1,749,575 5,709 1,921,772 1,916,310 5,462 contacts

  • tied
  • sliding

176 21 155 220 30 190 19 9 10 9 9 time step size 8.55e-4 ms 3.88e-4 ms 1.45e-4 ms 4.97e-5 ms

THUMS V1.x THUMS V3 THUMS V4

Model Variants and Versions

THUMS V4.02

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

  • Geometry (V1/3) and materials mainly from literature
  • Yamada H., Strength of Biological Materials, Williams & Wilkins Company, 1970
  • Clemente, C.D., Gray‘s Anatomy, 30th American Edition of the Anatomy of the Human body

by Henry Gray, Lea & Febiger, PA, 1985

  • Schneider, L.W. et al., Development of anthropometrically-based design specifications for an

advanced adult anthropomorphic dummy family, Volume 1, UMTRI-83-53-1, NHTSA, 1983

  • and others.
  • Experiments on human material ethically highly problematical
  • Standard-Pendulum tests validated by Cadaver Tests (Ethics?)
  • Thorax – lateral, frontal; Pelvis – lateral
  • Leg – lateral knee impact
  • Head/neck – lateral and frontal impact
  • Evaluation of test corridors, thus upper and lower bounds of experimental data, mainly in

the form of force-intrusion curves

  • Problem: Validation sources partly old and reliability/validity often unknown

THUMS Validation Basis

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

THUMS Modeling Details – Skeletal Structure

THUMS V3 + V4 occupant model THUMS V4 + V3 pedestrian models bone structure

  • trabecular bones (solids)
  • cortical bones (shells)
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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

THUMS V3/4 cranium THUMS V3/4 brain THUMS V1.x head THUMS V3/4 head THUMS V3/4 eye

THUMS Modeling Details – Head and Cranium

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH THUMS V3/V4 pedestrian thorax THUMS V3 + V4 pedestrian spine + thorax THUMS V3/4 vertebrae Source: Sobotta

THUMS Modeling Details – Spine and Thorax

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH Source: Sobotta THUMS V3/v4 pedestrian knee detail THUMS V3/V4 foot detail

THUMS Modeling Details – Lower Extremities

femural bone tibia and fibula bones knee with patella, meniscus and ligaments THUMS V3/V4 pelvis area

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THUMS Version 1.x/3.0 THUMS Version 4.0

  • coarse organ modelling in THUMS v1.x-3.0
  • due to coarse meshing and required model stability
  • (fine) organ modelling in THUMS version 4.0

THUMS Modeling Details – Internal Organs

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THUMS V3 from left and right side

different kinematical behaviour

THUMS V4 left impact and zoom on

stress distribution in lower extremities

Application Example – Pedestrian Model

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Occupant Barrier Impact – THUMS 3 vs THUMS 4

THUMS V3 impact from left total model and

zoom on shoulder belt

THUMS V4 impact from left total model and

zoom on shoulder belt

Application Example – Occupant Model

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Special Topic:

Model Shape Modification and Positioning

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

  • B. Allen, B. Curless, Y. Popovic: The space of human body shapes: Reconstruction and

parameterization from range scans, University of Washington, 2003

Model Positioning - Introduction / Motivation

2 areas of interest

  • model positioning
  • match different (non-standard) postures or seat geometries
  • necessary for virtually all load cases
  • model scaling/morphing
  • human models like THUMS available only in standard body size, shape

and posture (AM50, AM95, AF05, 6YO)

  • however: influence of individual body shapes is hardly accounted

for (skinny/obese body shapes, changes due to ageing)

  • standard body sizes may not be representative any more
  • necessary only sometimes, combines with positioning
  • Q: how to quickly modify available human models to

create different body shapes or postures?

AM50 THUMS v4 in standard postures example for posture change

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Model Positioning - Introduction / Motivation

Geometric Model adaptation rather than simulations

  • straight forward approach: use FE simulations
  • apply appropriate boundary conditions (impactors,

string pulling technique, etc.) to adapt the posture

  • perform simulations and grab desired position from

the result files

  • merge new nodal coordinates into original model file
  • however:
  • sometimes difficult to estimate required

boundary conditions -> iterative approach

  • can be time consuming and numerically expensive
  • mesh quality deteriorates after positioning simulation
  • > can lead to problems in actual crash simulation
  • use geometric smoothing procedures rather

than simulations

  • based on control-point based non-linear interpolation approach
  • apply constraints – e.g. translate/rotate body limbs to final position
  • use smoothing process on interfacial parts (joints, covering flesh/skin)
  • pure relocation of nodes, no change of the mesh connectivity
  • required: smoothing procedure to adapt deformable interfacial parts
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Interpolation Method – Problem Description

Mathematical Problem

  • required: control-point based interpolation of

multidimensional data with exact fit of data points

  • given: set of N data points xj (j=1,…,N) and corresponding

data values f(xj)

  • N is number of control points / landmarks
  • data points – nodal coordinates, data values – 3D displacements

λj – interpolation weights ψj – interpolation function

Example: ψj – linear: - NI iso-parametric shape functions used in FE analyses

  • interpolation via morphing (morphing boxes)
  • nly limited approximation possibilities using linear interpolation functions
  • no large local deformations can be realized
  • refine mesh or use higher order shape functions
  • choice of interpolation function (nonlinear)
  • radial basis functions - a real-valued radially symmetric function which

value only depends on the distance r to a given point

  • kriging approach - geostatistical technique, based on minimization of

a Lagrangian to compute weights λj

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Interpolation Method – Mathematical Background

Interpolation based on Radial Basis Functions Interpolation based on the Kriging Approach

  • choose
  • augmented RBF approach

with polynomial extension pk(x)

  • leads to linear equation system
  • possible radial basis functions
  • linear/cubic
  • “thin plate spline”
  • multiquadratic
  • simple theory/implementation
  • good results depending
  • n polynomial

extension

  • stable system

conditions

  • 1. minimize the scattering of the estimation error
  • 2. match of expected value

 minimize Lagrangian functional  leads to linear equation system for λ and μ  rearrangement leads to a dual formulation:

 matrix contains initial coordinates of control points  rhs contains new coordinates of control points

  • complex theory and implementation
  • very good results and stable
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Interpolation Method - Example

Test Example – interpolation of a test box motion

  • fixation at 20 nodes at the end of the box
  • displacement of two nodes in vertical-direction
  • test of different interpolation procedures
  • strong distortion for RBF interpolation with

constant extension

  • good results for tri-linear extension
  • best results: kriging + cubic RBFs

interpolation with constant extension interpolation with tri-linear extension fixation at 10 nodes fixation at 10 nodes given motion at 2 nodes

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Interpolation Approach - Full Interpolation

Holistic interpolation of the Thorax

  • control-point based interpolation of the whole thorax
  • required
  • good distribution of control points, avoid extrapolations
  • exact match of control points necessary, otherwise

local distortions -> very difficult

  • very fast and simple method to adapt the thorax
  • however good shaped elements difficult to obtain

and ensure

initial and interpolated THUMS thorax geometry rib cross section not retained control point distribution unrealistic sternum shape

  • holistic interpolation hardly suitable for FE analyses
  • unrealistic deformations / bad element shapes
  • highly depends on distribution of control points

deformation of the cervical spine

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  • apply multistep approach to adapt the geometry in different steps

*MOVE

move nodes/parts with

  • ptional smoothing

*SCALE

scale nodes/parts with

  • ptional smoothing

*SMOOTHING_PARTS smoothing of parts with given boundary conditions *PROJECT_NODES project nodes to given base part and transform nodal positions

*ALIGN

align parts according to the motion of two reference points

*ALIGN_CSYS

align parts according to the motion of a ref coordinate system

Interpolation Approach - Multi-Step Interpolation

Development of an Interpolation Tool Box

  • different geometric modification methods (Python)
  • create batch-based geometry adaptation process

*DEFINE_SEGMENT define (rigid) segment to be moved or aligned

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Multistep Interpolation of the Thorax

  • here: simplified parameterization of the thorax
  • statistic evaluation of a CT database
  • given: fix of sternum position and shape
  • given: thorax width in each rib plane
  • assumption: no spine deformation
  • automatic geometry adaptation using tool box
  • adaptation in 7 steps

1. sternum position and shape (given) 2. adaptation of rib base 3. fix thorax width (given) 4. reconstruct ribs (keep thickness and shape) 5. thoracic skin, flesh and organs 6. transitions to head, pelvis/abdomen 7. model fixes: remove contact penetrations, element distortions etc.

Multi-Step Thorax Interpolation

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Aktuelles von den THUMS Menschmodellen, Dirk Fressmann, 2016, DYNAmore GmbH

Step 1 – Adaptation of Sternum

  • given: points of sternum (s1-s7)
  • describe sternum position and shape
  • motion of sternum points and

smoothing process

initial and adapted geometry comparison RBF (cubic) and kriging

Multi-Step Thorax Interpolation

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Step 2 – Adaptation of Rib Basis

  • given: sternum motion
  • interpolation of rib basis and

inner costal pleura

  • sternum and vertebrae as control

parts (boundary conditions)

comparison RBF(cubic) and kriging initial and adapted geometry

Multi-Step Thorax Interpolation

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Step 3 – Fix of thorax width

  • given: new rib basis + sternum
  • adaptation of thorax in each

rib plane (nodal displacements)

  • interpolation of rib basis and inner

costal pleura, sternum and vertebrae as control points

comparison RBF (cubic) and kriging initial and adapted geometry

Multi-Step Thorax Interpolation

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Step 4 – Reconstruction of Rib Geometry

  • given: new rib base and sternum
  • reconstruction of rib
  • projection of “old” rib onto rib base

and reconstruction on “new” rib base

  • minimize of rib deformation
  • retain rib cross section

Multi-Step Thorax Interpolation

initial and adapted geometry

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Step 5 – Adaptation of the Thorax (flesh, skin, organs, shoulder belt)

  • given: new rib, sternum and vertebrae
  • adaptation of skin, flesh, organs and

shoulder belt using kriging

  • rib base and costal pleura as

control parts

Multi-Step Thorax Interpolation

initial and adapted geometry

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Step 6 – Adaptation of the transitions (neck/abdomen)

  • given: costal pleura and thorax flesh
  • kriging of neck and abdomen/pelvis parts

Summary

  • steps 1-6 can be performed automatically
  • variants possible by changing of

parameters in input file

  • model quality is very good

Multi-Step Thorax Interpolation

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Step 7 – Model Fixes

  • merge of new nodal coordinates into original model
  • fix of extreme element distortions (only few in abdomen)
  • fix of initial contact penetrations (only few)

Multi-Step Thorax Interpolation

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Some Remarks

  • dramatically risen interest in human body modelling in automotive industry
  • currently frequent use of old THUMS V3.0 model
  • primary concern: model kinematics in various crash situations → THUMS4 too detailed (expensive)
  • THUMS 3 model is easier to handle (numerically and biomechanically, validation issue)
  • THUMS V1-4 only passive models, THUMS V5 first active model → to be evaluated …
  • no injury criteria yet available for THUMS model(s)
  • direct simulation of injuries desirable, but difficult to realize (injury mechanisms, model validation)
  • validation only w.r.t. crash situations, rather than biomechanical injury mechanisms
  • we are still at the beginning of human body modelling in automotive applications !!!

Remarks & Outlook

Outlook

  • increase validation database for all body regions
  • increase biomechanical (user) knowledge required for result extraction
  • first step: establishment of a THUMS Users Community (TUC)
  • join forces in THUMS development, gather biomechanical knowledge and develop/establish

useable injury criteria

  • virtually all German automotive companies involved
  • first project finished, follow-up project in preparation
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The End …

Thank you for your Attention